以伽玛暴和超新星遗迹为探针对激波物理的研究

Diffusive shock acceleration has been widely believed to be the mechanism accounting for particle acceleration and hence the non-thermal radiation in all kinds of high energy astrophysical objects, however how it works is still not well understood from first principle. In this proposal, we combine observations/experiments closely with theories - - we analyze the observational results of high energy phenomena, especially gamma-ray bursts (GRBs) and supernovae, in order to investigate/constrain the physics of their emission regions, the microphysics of shock waves, and hence the diffusive shock acceleration processes. The pictures of gamma-ray burst and supernova shock waves are very clean, which makes them effective probes for shock physics. In this proposal, we will probe the microphysics of relativistic shocks by analyzing the observed properties of gamma-ray burst afterglows; we investigate the radiation mechanism, the physics in the emission region and the structure of the jets in GRBs by analyzing the wide-band observational results; we calculate the multi-band spectra from supernova remnants in the hadronic model, including the contribution from the secondary particles; we derive the shape of particle spectral energy distribution around the high energy cutoff, in order to distinct the letonic or hadronic origin of the TeV emission from young supernova remnants; we caculate the EeV neutrino emission from ultra-high energy cosmic ray sources which would help to probe the nature of the emission/acceleration region and help to identify the origins of >10EeV cosmic rays.

各种高能天体中普遍存在着激波加速过程产生高能粒子乃至非热辐射，但激波加速原理还不清楚。本项目把观测实验与理论紧密结合，通过对高能天体- - 特别是伽玛射线暴和超新星- - 观测结果进行理论分析来研究其中的辐射区物理条件、微观激波物理乃至激波加速过程。伽玛暴和超新星总体物理图像干净，分别存在着相对论和非相对论激波，将是研究激波物理的有效探针。本项目中，我们将通过伽玛暴余辉的辐射特征来限制激波的微观物理结构；通过伽玛暴宽能带的观测分析其辐射机制及辐射区的物理条件乃至喷流的结构；计算超新星中强子过程产生的辐射，特别是次级粒子再辐射；推导超新星激波中高能截止区域重子/轻子的能谱，以辨别TeV辐射的轻子或强子起源；计算极高能宇宙线源的EeV中微子辐射，用以探索其物理条件乃至直接证认宇宙线起源。

高能天体物理中，伽玛射线暴和超新星是两类剧烈的恒星爆炸产生的现象，都涉及了无碰撞激波形成，高能粒子加速和高能辐射的过程，对于研究缺乏了解的无碰撞激波工作原理，以及宇宙线起源等基本问题是很好的探针。本项目中我们结合已有的对这两类天体的高能观测结果，对激波微观物理，粒子加速过程和宇宙线及中微子起源这些未知之谜进行“探测”和限制。(1) 我们结合多波段观测，研究了伽玛暴激波物理，发现伽玛暴余辉中存在磁场在下游逐渐衰减的现象；如果瞬时辐射中也存在激波后磁场快速衰减，就能很好解释伽玛暴能谱较硬这一疑难问题；而内激波模型能很好解释瞬时光学辐射呈现的光学延迟现象，支持伽玛暴喷流组分为重子物质主导。(2) 我们分析超新星遗迹X射线数据，限制了激波加速能力，发现纯质子很难加速到PeV能区，支持宇宙线PeV膝区为重核主导；并发现硬X能谱需要非球对称激波来解释，支持超新星非球对称爆炸。(3) 结合PeV中微子探测结果和伽玛射线探测结果，我们分析了各种天体对PeV中微子的贡献，发现银河系、伽玛射线暴和活动星系核喷流不可能是PeV中微子主要起源，而星暴星系是已知天体中最可能起源。另外，由于暂现源方面理论和观测的快速发展，我们也探讨了暂变源天体物理中的几个问题，包括X射线暂现源发生率、射电暴宇宙学和微型潮汐瓦解现象等。